Truck cabs are composed of several body parts, including side panels, a rear panel, a bottom panel and a header. They are built to various different dimensions and specifications depending on whether the cab is a "day" cab or a "sleeper". The depth of space behind the driver may be 70 inches or more for sleepers and considerably less for the so-called day cabs which are designed without sleeping space. The task of assembling these body parts is arduous and time-consuming.